Cell Antenna output power question dbW to W

[tilt404]

I hope I have the correct forum for this question and I'm sorry if I'm in the wrong place. Some statistics finally went online for a group of 6 cell antennas that went up on the roof of my apartment a year or so ago. I only knew they were for Telus but nothing more.

I've added an attachment of the data for the 6 antennas. Three are operating at 1900MHz and 3 at 2100MHz. The power for all 6 ranges from 27.8dbW to 32.5dbW. I could never understand how dbW translated to W until I looked for conversions online but was a bit shocked when I saw around 30dbW equals 1kW.

So to think just 20 feet or so above me there are two high frequency antennas operating at 1kW is a bit disturbing. Could this be accurate? I've posted on the forums here before showing a photo of them when just one was installed, you can see here:

http://forums.radioreference.com/gre-scanners/276478-attenuator-psr800.html

I was just hoping to hear back from someone who has more knowledge about these antennas and the power they put out. It seems the others around me are using similar power output but 1kW seems so high to me when I can talk on my ham radio in the 70cm band, across the whole county here on 0.5W using my simple Diamond x50a antenna.

 

[puzzleriddle]

Ante\nnas do not put out power? they have DB gain etc

 

[n5ims]

Try this converter for your answer.

dBW Calculator

 

[mmckenna]

Yes.

But keep in mind a couple of things:
That power is spread across 5 MHz or 10MHz.
The antennas are directional. They cover about 120 degrees of horizontal and only a few degrees vertical.

There is a risk of having 1000 watts pointed at you in close range but while those antennas are 20 feet above you, the amount of power making it down to you is pretty small. The RF power from those systems are sent out in a well designed pattern covering area out away from the building you are in.

I certainly wouldn't want to spend any time sitting in front of one of those antennas, but I wouldn't have too much issue with one mounted 20 feet above me with a lot of building materials between me and it.

 

[tilt404]

Try this converter for your answer.

dBW Calculator

Thank you, bookmarked it. One I was using worked ok but not as simple.

 

[tilt404]

Yes.

But keep in mind a couple of things:
That power is spread across 5 MHz or 10MHz.
The antennas are directional. They cover about 120 degrees of horizontal and only a few degrees vertical.

There is a risk of having 1000 watts pointed at you in close range but while those antennas are 20 feet above you, the amount of power making it down to you is pretty small. The RF power from those systems are sent out in a well designed pattern covering area out away from the building you are in.

I certainly wouldn't want to spend any time sitting in front of one of those antennas, but I wouldn't have too much issue with one mounted 20 feet above me with a lot of building materials between me and it.

Thank you. I was wondering why my scanner hasn't fried from being so close to that much power but I guess its like you said, not directly at me but still so close. I never imagined they were using so much power. Ones on the other side of the roof are actually pointed at the other apartment in its path. I sure won't be sitting on the balcony any more. I moved my diamond antenna out there as far from them as I can to the other side of the balcony.

I see both are at least turned away from me. I face south and they are pointed south west. They have a pivot that seems like it can be controlled remotely and angle down slightly to the ground. I just find it so odd they can use so much power without any consent or meeting with the tenants at all though. Or education about them or information. I usually respect all transmission antennas, but now I have a much higher respect for cell tower antennas also.

 

[K5MPH]

Are theses cell tower antennas and if so I really don't think the would be pumping out 1kw of watts and dbw is not the same as pep watts you're info does not make sence ........

 

[kayn1n32008]

Are theses cell tower antennas and if so I really don't think the would be pumping out 1kw of watts and dbw is not the same as pep watts you're info does not make sence ........

Actually... If you have a 30w transmitter, tower mounted(all 3G and LTE stuff Telus uses is tower mounted) transceiver, with a really short feedline, and 14db gain antenna, 1KW ERP/EIRP is realistic.

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[zz0468]

Keep in mind that, while a transmitter may put out 100 watts to an antenna with 10db gain for a 1000 watt ERP, that's still just 100 watts of total power being radiated, not 1000. Your chart doesn't specify TPR or ERP, but in either case, you're not having to absorb anywhere close to a kilowatt in your head.

 

[tilt404]

Are theses cell tower antennas and if so I really don't think the would be pumping out 1kw of watts and dbw is not the same as pep watts you're info does not make sence ........

Canadian Cellular Towers Map

That was the site I used, each tower icon you click on will expand to give the details of it. It didn't show that the ones on my roof also are using frequencies in the 800mhz band though. Unfortunately the government frequency search site doesn't go over 1ghz. Other Tx sites though aren't close to these 1.9ghz or 2.1ghz dbW output. Other ones here in the 900mhz band that are tv or radio broadcasters are using slightly more but that is for wide area commercial broadcasting so it all doesn't make sense to me either.

The FM radio stations here are using similar power like the university radio station uses 33.2 dbW at 99.1mhz. Different frequency band I know than 2.1ghz but something just doesn't add up to me from the numbers on that site. Or I just don't understand how all this works for cell antennas with gain of the antenna and such. The transmitters are close to the antenna, only 10 feet away or less. Then they are linked to some dish through fiberoptic cable or something.

 

[kayn1n32008]

Telus(and likely Bell) are using tower mounted transceivers for UMTS/LTE. iDEN and CDMA/CDMA1x/EVDO are shack mounted transceivers with (usually) 1-5/8" hardline run up the tower. The only gear in the 'radio room' for UMTS/HSPA/LTE in Telus sites is the power supply, battery back up and network interface equipment. If the site is linked by microwave, those transceivers will be in the radio room.

Only power and fibre optics from the radio room go up the tower to the transceivers.

Likely the power figures you see on that site are EIRP/ERP, not transmitter power output.


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[tilt404]

Telus(and likely Bell) are using tower mounted transceivers, the only gear in the 'radio room' is the power supply, battery back up and network interface equipment. If the site is linked by microwave, those transceivers will be in the radio room.

Only power and fibre optics run from the radio room up the tower to the transceivers.

Likely the power figures you see on that site are EIRP/ERP, not transmitter power output.


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These are the transmitters I imagine that are mounted on a pole just behind the antennas, these are for the two cell antennas closest to me. That will be image 1275. Then there is a dish type of antenna behind them on the elevator bump up structure on the roof seen in image 1199. There are two cell antennas at each of the 3 corners of my roof, and one larger radio room they put up on the roof also.

I guess the cost of just electricity with 1kW going out across each of the 6 antennas up there would cost a fortune so like you said they probably mis labelled the power on that site which is why I was so confused.

 

[tilt404]

Telus(and likely Bell) are using tower mounted transceivers for UMTS/LTE. iDEN and CDMA/CDMA1x/EVDO are shack mounted transceivers with (usually) 1-5/8" hardline run up the tower. The only gear in the 'radio room' for UMTS/HSPA/LTE in Telus sites is the power supply, battery back up and network interface equipment. If the site is linked by microwave, those transceivers will be in the radio room.

Only power and fibre optics from the radio room go up the tower to the transceivers.

Likely the power figures you see on that site are EIRP/ERP, not transmitter power output.


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Here is a photo of the radio room also you mentioned from looking at street level up and how the groupings look, sets of 3 masts but they currently just have 2 antennas on each group.

 

[kayn1n32008]

A cell site has 3 sectors, each sector has a RX and TX antenna. They are multi band antennas, likely 800/1900/2100MHz(maybe 2500MHz depending on spectrum allocations where you live)


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[slicerwizard]

I guess the cost of just electricity with 1kW going out across each of the 6 antennas up there would cost a fortune so like you said they probably mis labelled the power on that site which is why I was so confused.

Hydro costs are the least of their worries. The monthly rent on all of the rooftops they occupy - now there's a scary bill.

 

[kayn1n32008]

These are the transmitters I imagine that are mounted on a pole just behind the antennas, these are for the two cell antennas closest to me. That will be image 1275. Then there is a dish type of antenna behind them on the elevator bump up structure on the roof seen in image 1199. There are two cell antennas at each of the 3 corners of my roof, and one larger radio room they put up on the roof also.



I guess the cost of just electricity with 1kW going out across each of the 6 antennas up there would cost a fortune so like you said they probably mis labelled the power on that site which is why I was so confused.

It not 6 antennas transmitting, only 3 of the 6. And the microwave antenna is likely back haul to another site that has fibre optics... UMTS/HSPS/LTE move way too much data to be copper fed.

 

[tilt404]

It not 6 antennas transmitting, only 3 of the 6. And the microwave antenna is likely back haul to another site that has fibre optics... UMTS/HSPS/LTE move way too much data to be copper fed.

Thanks, the info I keep getting from sites is misleading then how they say 6 are all transmitting at around 30dbW. There is another cell info site but you have to pay to use it. I do notice different/few cables go to each antenna though. A close up I have of one shows many connectors and has written each to the connectors for what band they are for.

 

[tilt404]

Hydro costs are the least of their worries. The monthly rent on all of the rooftops they occupy - now there's a scary bill.

I've been wondering about that also since in the public company that owns this building and posts their reports online, there's been no mention of income from this source. Makes me wonder where the money is going and who is getting it. I don't think they could be up there for free like you said.

 

[kayn1n32008]

Thanks, the info I keep getting from sites is misleading then how they say 6 are all transmitting at around 30dbW. There is another cell info site but you have to pay to use it. I do notice different/few cables go to each antenna though. A close up I have of one shows many connectors and has written each to the connectors for what band they are for.

Let me rephrase that. Each sector (direction a pair of antennas face) will have multiple bands on each of the two antennas. One is transmit, one is receive. So you will see 3 bands, with each band having 3 azimuths. While the site has 6 antennas, 2 for each sector.


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[mmckenna]

Often there are two polarizations on each sector antenna for each frequency: +45˚ and -45˚ Each one is fed with a separate coaxial cable. Each antenna often has two or more bands. It's not uncommon to see 4 or 6 port antennas depending on the carrier.
There is often a separate cable for electronic or "remote" down-tilt control. Some cell sites have the ability to remotely tilt the antenna pattern electronically.
A full traditional cell site can have a bunch of coaxial cable on them. More modern systems using RRU's (remote radio units) mount the radios at the base of the antennas and just route fiber optic and power from the hut to the antennas. Saves a boat load on coaxial cable, reduces the feed line losses, and can reduce windloading on the tower. All that coax cabler running up the tower legs catches a lot of wind and has to be figured into the tower design.